For the heart to function regularly, it has a natural pacemaker with wires. There are two junctions where the wires meet. One is near right atrium (Sino–Atrial node) and other is near junction of atria and ventricles (atrio-ventricular node). Wires connect the junctions to atria and ventricles.

During aortic, mitral, tricuspid valve surgery, it involves operating very close to these structures. Anatomy varies from patient to patient. At times, inflammation and incision near these structure render the natural pacemaker system non-functional either temporarily or permanent. If there is no recovery or incomplete recovery, patient requires a permanent pacemaker insertion.